This invention relates generally to flow regulating devices, and more particularly to industrial valves of a type wherein the flow of fluid is regulated by selectively positioning a flexible diaphragm relative to a stationary port opening in the valve assembly body. One such valve, which utilizes a flexible diaphragm selectively positionable relative to a stationary weir, is described and claimed in U.S. Pat. No. 3,250,511.
Modern valve design encourages the construction of low cost, effective, long-life valves which can be used in a wide variety of applications and under a wide variety of operating conditions. In industrial uses, fluid line pressures on the order of 300 PSIG or higher and temperatures in the range of 150.degree. to 250.degree. F. can be encountered. When valves are employed in the regulation of fluid flows in the nuclear power industry, component valve parts can be exposed to the effects of gamma radiation, which can degrade the performance and service life of some valve parts. Valve body and diaphragm parts may also be contacted and wetted by service fluids and gases, at least some of which can adversely affect the operation or service life of valve parts. In addition valves must withstand mechanical forces and shocks without damage or wear, and their continued proper operation must be assured for specified periods of time. These forces can be caused by high hydrostatic line pressure loads, thermal cyclic forces, seismic disturbance loads applied either directly to the valve itself or to parts or lines connected to the valve, and the like. Further difficulties are encountered when several of these forces act upon the valve so as to produce additive effects.
In an effort to promote safety and proper operating characteristics, construction codes and regulations now specify performance, service life and other parameters for valves and other components commonly used within the nuclear power industry. Implementation of these codes restricts the utility of some valves and other components widely used elsewhere, and presents additional problems for valve designers.
Experience with valves of this general sort has shown that repeated valve operation and elastomeric diaphragm compression "set" will occasionally cause the valve diaphragm to relax or rock loose; i.e., repeated flexing or relaxation motions of the diaphragm causes the diaphragm edge to pull away from its position relative to seating or restraining portions of the valve assembly, thereby causing premature valve leakage, and potential valve failure by unacceptable outleakage to the atmosphere.
Many of these problems can be ameliorated if not entirely overcome by providing a valve in which internal stress intensity levels are reduced or eliminated in component parts and part assemblies. To this end, the major internal stresses are encountered when the valve is in the open condition and the diaphragm is subjected to the line pressure. With the present invention the valve housing and diaphragm compressor are designed to provide full and complete support over substantially the entire area of the diaphragm. Accordingly, any danger of the diaphragm ballooning outwardly and being cut or damaged by sharp corners or edges on the valve components is precluded. Also, the diaphragm of the present invention is molded in the valve open condition, clearly reducing internal stresses when the diaphragm encounters high line pressure while in service.
It thus is the general object of the present invention to provide a new and improved diaphragm type valve which is designed and arranged to provide relatively reduced stress intensity levels in its component parts.
Another object of the invention is to provide a low-stress valve mechanism which positively prevents overclosure and crushing of the resilient valve diaphragm when the diaphragm is moved into a valve-closed position.
Yet another object of the invention is to provide a low-stress valve mechanism of the type described which can be used with a handwheel-operated valve or with a valve having alternative mechanisms for valve operations.
It is another specific object of the invention to provide a low-stress valve construction which will prevent rocking motion of the flexible diaphragm from ultimately working the valve diaphragm periphery out of or away from its proper seat on retaining valve parts, thereby loosening the diaphragm and causing premature valve failure.
Another object of the present invention is to provide a new and improved diaphragm type valve which will provide extended service life under the conditions described, yet which can be provided at an attractive commercial cost.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings. Throughout the description, like reference numerals refer to like parts.